The effect and mechanism for doping concentration of Mg-Hf on the piezoelectric properties for AlN

The piezoelectric coefficient of intrinsic AlN is not meeting the demand from some high-performance applications in MEMS compared with the commercialized piezoelectric ceramics. Therefore, we conducted a first principles calculation investigation of the piezoelectric properties of Mg-Hf co-doped AlN structures with the same doping proportion (Mg x/2Hf x/2Al1-x N) to further improve the performance of AlN materials. The analysis results suggested the co-doped structures show decreased band gap values with a non-symmetrical charges assignation. Consequently, both the elastic constant C (33) and Young's modulus are largely reduced. Furthermore, the co-doped structure shows a drastically improved piezoelectric coefficient d (33) compared with intrinsic AlN.